ROOTCASTLE / LABORATORI ENGINEERING
Lab Keandalan
MTBF, umur Weibull lan matematika redundansi.
LOCAL CALCULATION · EDUCATIONAL MODEL
MTBF and availability
- Mission reliability R(t)
- 64.53 %
- Expected failures in mission
- 0.438
- Availability A
- 99.96 %
- Number of nines
- 3.4
- Expected downtime per year
- 3.5 h
- λ · FIT
- 5.00e-5 /h · 50,000
Model and assumptions
Constant failure rate (exponential distribution): R(t) = e^(−t/MTBF), λ = 1/MTBF. Inherent availability A = MTBF/(MTBF+MTTR); logistics and waiting time are not included. The probability of surviving to the MTBF is always 36.8 %: MTBF is not a guaranteed life.
R(t) = e^(−t/MTBF); A = MTBF / (MTBF + MTTR); downtime = (1 − A) · 8760 h
Untuk apa
Kanggo nemtokake angka sing padha nalika ngobrol bab berapa lama alat bakal mati taun, apa sing bener dibeli dening unit redundan, utawa nalika wektu ganti siji bagian kudu dimulai. Matematika MTBF, Weibull lan redundan ditampilkan karo persamaan; ganti asumsi lan lihat sensitivitas hasil.
Kaslahan
Angka MTBF pabrik umoroé prediksi kanggo suhu lan beban sing ditetepi; kondisi lapangan sing beda-beda nyebabake resulta sing beda-beda. Matematika redundansi ngasumsi satuan gagal mandiri; penyebab umum kayata sumber daya sing padha, bug software sing padha utawa kesalahan perawatan sing padha ngurangi manfaat nyata. Fungsi kalebut kudu ditiliti karo asesmen sing beda menurut IEC 61508 / ISO 13849.
References
IEC 61703:2016 (mathematical expressions for reliability, availability, maintainability) · IEC 61649:2008 (Weibull analysis) · P. D. T. O’Connor, A. Kleyner, Teknik Keandalan Praktis, ed. 5 · NIST/SEMATECH e-Handbook, Assessing Product Reliability
Model pendidikan. Hasilnya tidak cukup untuk merusak mesin atau menetapkan batas operasi yang aman.